Pterosaurs—Lords of the Ancient Skies

Thursday, March 10, 2011

Three flying reptiles from Earth's distant past glide above the gray Pacific, far beyond the rollers breaking on the shore of Point Reyes, California. They flap their wings slowly for a few beats, gain some altitude, then turn toward the beach. One peels out of formation and dives into the water with a splash, sinking just as far as its shoulders to snatch a fish with its long snout. Then, with a few powerful wing strokes, the beast takes off, using its webbed feet to hop off the waves until it clears the water. As it draws near, the primeval pterosaur transforms into an ordinary brown pelican.

Keven Padian, a paleontologist at the University of California, Berkeley, stands on the beach gazing at the birds through binoculars. Watching coastal birds helps Padian envision the time when pterosaurs occupied the same ecological niche, plunging for fish like pelicans, soaring like gulls, and pecking at the sand like sandpipers.

"Pterosaurs were just the coolest things that were ever in the air," says Padian. "They were the first vertebrates to fly. They did it long before birds and bats. And it terms of size, they pushed the envelope as far as it could go for a flying animal."

Like their cousins the dinosaurs, pterosaurs stand out as one of evolution's great success stories. They first appeared during the Triassic period, 215 million years ago, and thrived for 150 million years before going extinct at the end of the Cretaceous period. Their endurance record is almost inconceivable compared with the span of humans, whose ancestors started walking upright less than four million years ago. Uncontested in the air, pterosaurs colonized all continents and evolved a vast array of shapes and sizes. Of more than 120 named species, the smallest pterosaur measured no bigger than a sparrow; the largest reached a wingspan of nearly 40 feet (12 meters), wider than an F-16 fighter.

Until recently most paleontologists would not have put pterosaurs in the same league as birds in terms of flying ability. Because pterosaurs were reptiles, generations of scientists imagined that these creatures must have been cold-blooded, like modern snakes and lizards, making them awkward aerialists at best.

In the past three decades, however, a surge of fossil discoveries around the globe has prompted researchers to reexamine their views. The emerging picture of pterosaurs reveals that they were unlike any modern reptile. From a fossil discovered in Kazakhstan, paleontologists suspect that pterosaurs had a hairlike covering, perhaps akin to fur. If so, this detail provides evidence of a high-revving, warm-blooded physiology that could sustain the kind of exertion needed to stay in the air. Judging from the skulls of other fossils, scientists reason that many pterosaurs were gifted air-borne predators, built to feed on the wing. They darted after insects, dive-bombed for fish, and soared hundreds of miles over open ocean on extended hunting expeditions.

"For about 150 years pterosaurs were regarded as typical slow-moving, cold-blooded reptiles. People had the idea that pterosaurs could glide, but they couldn't flap their wings," explains Alexander Kellner, a Brazilian paleontologist. "We thought they couldn't take off from the ground."

Pterosaurs first grabbed Kellner's attention when he was a child in Rio de Janeiro, where he became hooked on a television cartoon featuring one. His early fascination might have foundered, but when Kellner was a student, Brazilian scientists started to uncover a mother lode of pterosaur fossils in the northeastern part of the country, on the slopes of the Araripe Plateau. In the past 30 years Araripe has yielded remains of 19 new species, an unrivaled pace of discovery.

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